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Fiberglass Parts FAQ
An Overview of Fiberglass Parts
  Replacement and customized body parts have been fundamental to Superior Glass Works since our beginning back in 1976. Superior Glass Works is the premier manufacturer of Chevy fiberglass with more than 500 parts available for Chevy passenger cars and trucks produced from 1931-1955. Many Ford parts are also available for 1928-1934 cars.  We also manufacture 25 fiberglass and carbon fiber street rod and race car bodies, as well as non-automotive parts for many other industries.
How fiberglass parts are made
  All Superior Glass Works parts are made via an open-mold, hand-laid production method.  This starts with a mold that is the negative image of the part to be made. Due to the complex shape of most of these parts, the molds are made with flanges that bolt together, and conversely, unbolt to remove the part from the mold.  Into this mold we spray black, sandable gelcoat which becomes the finished surface of the end product you will receive.  Catalyzed, polyester resin is applied to the mold, alternating with three layers of 1.5oz fiberglass mat added by hand.  As each layer is applied, all air is rolled out by hand to insure a strong, defect-free part.  We NEVER use a chopper gun to make any of our rod or race parts or bodies!
Parts Fitment
  All Superior Glass Works’ molds were created from original pieces and the parts produced are guaranteed to install on to stock, steel cars and reproduction bodies just as a new old stock (NOS) piece will. Keep in mind, however, that when working on a 60+ year-old vehicle, some massaging may be required for a proper fit. This is no different than original or NOS steel parts, and inconsistencies in original parts and bodies are common for this generation of vehicle.  Additionally, repairs made to steel bodies and parts i.e. welding in patch panels, tail pans, fixing rotted rockers, etc. can all change your vehicle from the original dimensions.
• “My original part is smaller/shorter than my new fiberglass part. Why?” – When a fiberglass part is removed from the mold, it may relax and ‘open up’ a little and is particularly noticeable on larger parts like front fenders and hoods.  One of the great properties of fiberglass is its flexibility.  This allows it to move back into shape upon installation.
• “I can’t get the fender to fit in the wheel opening.  How can I get it to fit?” – We recommend starting at one end of the fender and working bolt-by-bolt along its radius.  This allows you to gradually move it into the shape of the wheel opening.  Be careful not to overstress the fiberglass or try to draw it in with a bolt as this may cause cracking.  You can use a heat gun to gain even more flexibility, but we rarely use this technique.
Prep for Painting
  The gelcoat is intended to be block-sanded and primed just as you would a steel part.  Mold seems or other imperfections can be filled with any skim coat, icing, or body filler product.  In the event that you do need to add additional fiberglass or wish to modify the part, be certain to use a polyester resin, NOT epoxy resin.
Preventing starring of fenders
  The most effective way to prevent starring is to only drive your car in and out of a trailer, and never drive it on the road. If this is not possible, then there are two preventative measures you can take.  First, proper paint prep and paint adhesion is critical.  (See above.)  Secondly, applying an undercoating under the fender will help reduce the impact of anything coming off your tires.  It is recommended that a true undercoating is used (3M makes a good one) rather than truck bedliner material as the later can be heavy and flammable.
Why is there a ridge line through the middle of my part?
  This line is known as a mold seem, parting line, and/or flange line.  Where the multiple parts of the mold bolts together, some of the black gelcoat will seep into this seam when it is applied.  When the part is removed from the mold, this seem is visible in the gelcoat surface of the finished part.  As a mold is used over and over, these mold flanges will sometimes develop small chips, which can also be visible in the final part.  To minimize the appearance of this flange line, we fill the seam and any chips with clay before spraying the gelcoat.  Although we clean each part before it is shipped, there may still be some residual clay left on the part.  
• “Why is there an unfinished line where my part was glued together?” – What you are seeing is the mold seam.  All of our parts are made in a single mold as one piece.  Only our decklids are glued together, as needed to bond the outer skin to the inner decklid panel.
• “Why can I see light through the mold seem?” – When removing a part from the mold, sometimes a small bit of gelcoat will stick to the mold in the area of the flange, allowing light to get through the opaque fiberglass underneath.  The gelcoat adds no strength or structure to the finished part, and this seam will be body worked and filled prior to paint.  If you see light through another area of the part, the gelcoat was applied a little thin in that spot.  It does not indicate any structural issues or weakness in the fiberglass  itself.
Yes! We do custom work!
  Need a scoop added to the hood? Kiss the wall with your 'glass-nosed race car? Put your Jeep on its side?  Our composites experts can create custom fiberglass parts, and modify or repair your existing fiberglass parts or body.  And we aren't limited to automotive applications, as we have worked for businesses across many industries such as aerospace, construction, transportation, military and communications.  Click here for more information about the services we offer.

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